The invention relates to a method for producing a multiaxial structure out of multifilament threads according to the precharacterizing clause of the main claim.
1. Field of the Invention
A device for producing a multiaxial structure out of multifilament thread has been known, for example, from the piece in the literature xe2x80x9cRationalisierung der Fertigung langfaserverstxc3xa4rkter Verbundwerkstoffe durch der Einsatz multiaxialer Gelegexe2x80x9d [xe2x80x9cRationalization of the production of long-fiber-reinforced composite material through the application of multiaxial structuresxe2x80x9d] by Karlheinz Hxc3x6brsting, Verlag Shaker, Aachen 1954, in particular pages 30 and 32.
2. Background of the Invention
The manner of functioning of such a machine shall be briefly described in the following, in order to improve the understanding of the invention:
The multifilament threads are drawn from bobbin creels and fed to weft iserton carriages that move on adjustable rails ad place the multifilament threads, in the required orientation of xc2x125xc2x0 to 90xc2x0, into a so-called needle-transport chain. On each weft insertion carriage the density of the supplied threads can be set by means of a reed comb, thus determining the weight per m2 of the individual layers. For the exact inlaying of the needle-transport chains, the weft insertion carriage swings out over the transport chain in the edge region. Upon barking at the reversal point, the excess-supplied material is compensated though a thread storage device. Through an appropriate movement the multifilament threads are pressed behind the needles of the transport chain. In order to ensure a parallel laying down of the multifilament threads, the combs of the weft insertion carriage performs an offsetting movement in the production direction, corresponding to the strip width of the threads. After the offsetting movement, the weft insertion ends carriage and travels toward the opposite side of the structure.
Through the sequential operation of several weft insertion systems, the structure is then stratified in different orientations.
The 0xc2x0 filaments-which thus extend in the production direction are inserted directly from a warp beam or an additional bobbin creel immediately in front of a knitting or stitching machine.
The loose thread structure is fixed by means of a conventional knitting or stitching machine. Subsequently the edge regions of the structure, which lie in a transport chain, are then cut off, since thread damage to tight filament curvatures is present here. The finished multiaxial structure is then wound onto a cloth roller.
The weft multifilaments are laid down, at an angle of xc2x122.5xc2x0 to xc2x160xc2x0 and more, seen in the production direction and in a 90xc2x0 direction, while the so-called warp threads are fed in the 0xc2x0 direction, i.e. parallel to the production direction.
At present the so called multifilaments of the 0xc2x0 layer always form the top layer of the completed multiaxial.
Such multiaxial structures frequently consist of multifilaments produced from which are highly sensitive to bending and fracture, and if the 0xc2x0 multifilaments are arranged in the top layer the winding of the finished structure onto the cloth roller leads, to an overstressing of the fibers of these multifilament threads. Thus, in the case of a multiaxial structure composing a multiplicity of individual layers, for example six or seven layers, until now the following procedure was followed: one produced structures with, for example, three layers, in which the 0xc2x0 multifilaments were also arranged in the topmost layer, and then turned around one of these structures, so that then two structures were superimposed, in which the 0xc2x0 multifilaments were arranged in the middle, thus theoretically in the so-called neutral zone; then, these structures, already stitched once, were stitched a third time, i.e., the two structures had to be stitched together. This led to the fact that through the several courses of stitching additional damage occurred to the fibers of the multifilaments.
From DE 39 10 245 A1 has been known a process and a device for producing a thread lattice. In order to achieve an extensive isotropy of the thread lattice, it is here proposed that, above, below, or between the individual groups of the threads that are already laid down and run in the transverse direction as well as the in the diagonal direction, in addition threads be introduced in the longitudinal direction. The supplying of the longitudinal-direction, thus the 0xc2x0 threads, immediately in front of the stitching location is not possible when the 0xc2x0 threads are to be laid between the individual cross-threads. These 0xc2x0 threads, supplied at any location whatever, do not, however, retain their aimed-for position and desired distribution, but rather shift, so that different thicknesses and thus different strengths, considered in the transverse direction of the structure, necessarily come about.
The object of the invention is to create a multiaxial structure in which it is possible to supply the 0xc2x0 multifilaments threads at any location of the structure, to secure their predetermined position, and in spite of this to produce a structure that is composed, for example, of seven layers, but needs to be stitched only a single time.
This object of the invention is achieved through the teaching of the main claim.
Thus, proposed is a multiaxial structure with, for example, seven layers, in which the 0xc2x0 layers can be worked in between the other xc2x122.5xc2x0 to 90xc2x0 layers, and are held secure in their aimed-for alignment, position, and distribution.